Method and device for improved salicide resistance on polysilicon gates

Abstract

A method and device for improved salicide resistance in polysilicon gates under 0.20 μm. The several embodiments of the invention provide for formation of gate electrode structures with recessed and partially recessed spacers. One embodiment, provides a gate electrode structure with recessed thick inner spacers and thick outer spacers. Another embodiment provides a gate electrode structure with recessed thin inner spacers and recessed thick outer spacers. Another embodiment provides a gate electrode structure with thin inner spacers and partially recessed outer spacers. Another embodiment provides a gate electrode structure with two spacer stacks. The outermost spacer stack with recessed thin inner spacers and recessed thick outer spacers. The inner spacer stack with thin inner spacers and thin outer spacers. Another embodiment provides a gate electrode structure with two spacer stacks. The outermost spacer stack with recessed thin inner spacers and recessed thick outer spacers. The inner spacer stack with recessed thin inner spacers and recessed thin outer spacers.

What is claimed is:  
     
       1. A method for forming a gate electrode comprising the steps of: 
       providing a substrate with an insulative layer deposited thereon;  
       forming a gate layer on the insulative layer;  
       depositing a thin first spacer layer on the gate layer and the substrate;  
       depositing a thin second spacer layer on the thin first spacer layer;  
       removing a portion of the thin second spacer layer to form thin second spacers;  
       removing a portion of the thin first spacer layer to form thin first spacers;  
       depositing a thin third spacer layer on the gate layer, the thin first spacers and the thin second spacers;  
       depositing a thick fourth spacer layer on the thin third spacer layer;  
       removing a portion of the thick fourth spacer layer to form recessed thick fourth spacers;  
       removing a portion of the thin third spacer layer to form recessed third spacers;  
       forming a protective layer on the substrate and gate layer;  
       removing a portion of the thin second spacers to form recessed thin second spacers;  
       removing the protective layer and removing a portion of the thin first spacers to form recessed thin first spacers;  
       depositing a layer of reactant on the gate layer;  
       annealing the layer of reactant and the gate layer to form a conductive layer; and,  
       removing the unreacted reactant layer.  
     
     
       2. The method of claim  1  wherein removing a portion of the thin second spacer layer to form thin second spacers is by anisotropic etching. 
     
     
       3. The method of claim  2  wherein removing a portion of the thin first spacer layer to form thin first spacers is by anisotropic etching. 
     
     
       4. The method of claim  3  wherein removing a portion of the thick fourth spacer layer to form recessed thick fourth spacers further comprises: 
       removing a first portion of the thick fourth spacer layer by anisotropic etching; and,  
       removing a second portion of the thick fourth spacer layer by isotropic etching.  
     
     
       5. The method of claim  4  wherein removing a portion of the thin third spacer layer to form recessed thin third spacers is by anisotropic etching. 
     
     
       6. The method of claim  5  wherein removing a portion of the thin second spacers to form recessed thin second spacers is by isotropic etching. 
     
     
       7. The method of claim  6  wherein removing the protective layer and removing a portion of the thin first spacers to form recessed thin first spacers is by isotropic etching. 
     
     
       8. The method of claim  7  wherein the insulative layer is an oxide. 
     
     
       9. The method of claim  8  wherein the gate layer is a polysilicon. 
     
     
       10. The method of claim  9  wherein the reactant is a metal. 
     
     
       11. The method of claim  10  wherein the thin first spacer layer is an oxide. 
     
     
       12. The method of claim  11  wherein the thin second spacer layer is a nitride. 
     
     
       13. The method of claim  12  wherein the thin third spacer layer is an oxide. 
     
     
       14. The method of claim  13  wherein the thick fourth spacer layer is a nitride. 
     
     
       15. The method of claim  14  wherein the protective layer is an oxide. 
     
     
       16. The method of claim  14  wherein the conductive layer is a polycide. 
     
     
       17. The method of claim  16  wherein the metal is titanium. 
     
     
       18. The method of claim  17  wherein the polycide is titanium salicide (TiSi 2 ). 
     
     
       19. A method for forming a gate electrode comprising the steps of: 
       providing a substrate with an insulative layer deposited thereon;  
       forming a gate layer on the insulative layer;  
       depositing a thin first spacer layer on the gate layer and the substrate;  
       depositing a thin second spacer layer on the thin first spacer layer;  
       removing a portion of the thin second spacer layer to form thin second spacers;  
       removing a portion of the thin first spacer layer to form thin first spacers;  
       depositing a thin third spacer layer on the gate layer, the thin first spacers and the thin second spacers;  
       depositing a thick fourth spacer layer on the thin third spacer layer;  
       removing a portion of the thick fourth spacer layer to form recessed thick fourth spacers;  
       removing a portion of the thin third spacer layer to form recessed third spacers;  
       removing a portion of the thin second spacers to form recessed thin second spacers;  
       removing a portion of the thin first spacers to form recessed thin first spacers;  
       depositing a layer of reactant on the gate layer;  
       annealing the layer of reactant and the gate layer to form a conductive layer; and,  
       removing the unreacted reactant layer.  
     
     
       20. The method of claim  19  wherein removing a portion of the thin second spacer layer to form thin second spacers is by anisotropic etching. 
     
     
       21. The method of claim  20  wherein removing a portion of the thin first spacer layer to form thin first spacers is by anisotropic etching. 
     
     
       22. The method of claim  21  wherein removing a portion of the thick fourth spacer layer to form recessed thick fourth spacers further comprises: 
       removing a first portion of the thick fourth spacer layer by anisotropic etching; and,  
       removing a second portion of the thick fourth spacer layer by isotropic etching.  
     
     
       23. The method of claim  22  wherein removing a portion of the thin third spacer layer to form recessed thin third spacers is by anisotropic etching. 
     
     
       24. The method of claim  23  wherein removing a portion of the thin second spacers to form recessed thin second spacers is by isotropic etching. 
     
     
       25. The method of claim  24  wherein removing a portion of the thin first spacers to form recessed thin first spacers is by isotropic etching. 
     
     
       26. The method of claim  25  wherein the insulative layer is an oxide. 
     
     
       27. The method of claim  26  wherein the gate layer is a polysilicon. 
     
     
       28. The method of claim  27  wherein the reactant is a metal. 
     
     
       29. The method of claim  25  wherein the thin first spacer layer is an oxide. 
     
     
       30. The method of claim  29  wherein the thin second spacer layer is a nitride. 
     
     
       31. The method of claim  30  wherein the thin third spacer layer is an oxide. 
     
     
       32. The method of claim  31  wherein the thick fourth spacer layer is a nitride. 
     
     
       33. The method of claim  32  wherein the conductive layer is a polycide. 
     
     
       34. The method of claim  33  wherein the metal is titanium. 
     
     
       35. The method of claim  34  wherein the polycide is titanium salicide (TiSi 2 ).